The present invention is directed to a method for the stabilization of polyoxyalkylene polyether polyols and to the use of the stabilized polyol in the preparation of polyurethane foams. In particular, the invention relates to the heat and oxidation stabilization of polyoxyalkylene polyether polyols with certain synergistic stabilizing compositions and the color and/or scorch stabilization of polyurethane foams made from the polyols by reaction with an organic polyisocyanate.
Prior art methods for the oxidative stabilization of polyoxyalkylene polyether polyols and for the use of such antioxidant-containing polyether polyols in the preparation of polyurethane foams to inhibit scorch are well known.
U.S. Pat. No. 3,428,567 discloses a stabilizer for polyols and halogenated lower aliphatic hydrocarbons consisting of phenothiazine. U.S. Pat. No. 3,437,694 teaches the use of 2,6-di-t-butyl-4-methylphenol and 2,4-dimethyl-6-t-butylphenol as polyol stabilizers. U.S. Pat. No. 3,567,664 discloses the stabilization of polyurethane foams against scorch when a mixture of p,p'-dialkyl diphenyl amine and 2,6-ditertiary-butyl-4-methyl phenol is present in a foam forming reaction mixture. U.S. Pat. No. 3,637,865 shows the polyether polyols stabilized against oxidation with a mixture of 2,6-ditertiary-butyl-4-methyl phenol and p,p'-dialkyl diphenyl amine. U.S. Pat. No. 4,007,230 teaches the stabilization of polyether polyols using a mixture of certain hindered phenols such as 2,4-dimethyl-6-octyl phenol and 4,4'-bis(.alpha.,.alpha.-dimethylbenzyl) diphenyl amine as well as to prevent scorch in polyurethanes. U.S. Pat. No. 4,228,247 discloses a mixture of 2,6-ditertiary-butyl-4-methyl phenol with amines such as p,p'-dioctyl diphenylamine or 4,4'-bis(.alpha.,.alpha.-dimethyl benzyl)diphenylamine, a phosphite such as phenyldidecylphosphite and 3,5-di-tertiary-butyl-4-hydroxyhydrocinnamate acid triester of 1,3,5-tris(2-hydroxyether)-5-triazine-2,4,6-(1H,3H, 5H)trione. U.S. Pat. No. 4,265,783 shows polyols stabilized against oxidative degradation with a combination of sterically hindered phenols, 4,4'-bis-(.alpha.,.alpha.-dimethylbenzyl)diphenylamine and phenothiazine. There is no teaching in the prior art of the synergistic effect obtained by stabilizing polyether polyols with the composition of the instant invention.